in reply to regex: something...(!something)...something
My tutorial on look-ahead and look-behind covers this.
You're specifying that the open tag is not followed immediately by another open tag; you want to specify that it's followed by any arbitrary text that isn't an open tag. This s/// expression should do what you want:
Caution: Contents may have been coded under pressure.
Update: I should have broken this down in commented style (I also note that I could have done lookahead for everything after the 3):$x =~ s{(?<=<td>)((?:(?!<td>).)*)3((?:(?!</td>).)*)(?=</td>)}{$1a$2};
$x =~ s{(?<=<td>) # Start match with open-tag ( # Capture (?:(?!<td>).)* # Any number of characters that do not star +t an open-tag )3 # Close capture; match literal 3 (?= # Look ahead to match (?:(?!</td>).)* # Any number of characters that do not star +t a close-tag </td> # then a close-tag )} # End lookahead and pattern {$1a}x;
Caution: Contents may have been coded under pressure.
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